The present invention relates to an optical coupler using optical communication. In the present invention, the optical coupler distributes a signal input from an arbitrary optical input terminal to all optical output terminals. The output from each optical output may have a different dissipation. When an optical input terminal and an optical output terminal serve as a pair, a signal input from the optical input terminal forming the pair may or may not be output to the optical output terminal forming the pair therewith. The optical input and output ends serving as the pair may include an optical input/output terminal as one integrated optical terminal.
There are many attempts to apply an optical communication technology to a LAN technology constructed in homes or transportation vehicles such as an automobile, electric train, aircraft, ship, etc. Here, an optical coupler is required to distribute and output a signal input from an arbitrary input end to all optical output terminals with a low dissipation amount. For example, the optical coupler is concisely described in a non-patent document of Fuji Xerox Co. Ltd, Technical Report, 1996, No. 1 (http://www.fujixerox.co.jp/company/tr/tr96/Takshi_Ota/T_Ota101.html).
On the other hand, the applicants of the present invention have developed and filed a plurality of self-forming optical waveguides using a photo-curable resin liquid. In these technologies, when curing light of the resin liquid is radiated from an optical fiber, etc., the concentration of light is generated by the curable resin and a core is formed on a long axis. These technologies are included in Patent Documents JP-4011283, JP-2002-365459, JP-2004-149579, JP-2005-347441, JP-2001-154046, etc.
As an optical coupler manufacturing method, a method based on the fusion of a glass fiber is widely known. However, a device for fusing the glass fiber is expensive. The manufacturing process is complex and time-consuming. As a result, an optical coupler by the glass fiber fusion is very expensive. In addition, the optical coupler by the glass fiber fusion is not easily connected to a plastic optical fiber (POF) used in a small-scale LAN.
The optical coupler using the plastic optical fiber (POF) is also known. However, this is only a plastic optical fiber (POF) bundle. Only a large optical coupler is known as a device forming an optical LAN. Its size is, for example, about 7 cm.
On the other hand, the inventors has completed a new optical coupler shown below as a result of active efforts to develop an optical coupler as an application of the self-forming optical waveguide shown in the above-mentioned patent documents. The optical coupler of the present invention is based on a new manufacturing method and, more particularly, can be easily manufactured by applying a method of manufacturing the self-forming optical waveguide.